For electronic board assembly, automated component placement can reach very high speed up to tens of thousands of surface mounts of components per hour. These components are typically supplied by component vendors as taped reels of components which are loaded onto individual feeders which then are mounted in corresponding feeder slots on the machine. These reels of components may be loaded onto the feeders at a special loading unit, for example in a stock room, after which the loaded feeders are placed in the feeder slots.
Component placement machines can have more than 100 feeder slots each accessible by a picking mechanism that picks individual components from the feeders in the slots and places them in particular predetermined locations on a printed circuit board. For application flexibility, each feeder and slot is generally constructed to be compatible with many different components.
The physical arrangement of components, feeders and slots must be in accordance with the expected arrangement as programmed in the machine. Any error in the arrangement can cause a corresponding error in the placement of components on the board. In a high volume, low mix manufacturing environment, a component loading error can produce a high number of defective printed circuit boards in a short period of time. In a low volume, high mix environment the chance of component loading error increases because of frequent feeder manipulation for product change over.
In order to eliminate loading errors, it is known to place bar code labels on individual feeders and slots for manual scanning to control that the right components indeed are placed in the right slots according to a so called device list, which contains a listing of the slots and the components that are expected in the different slots. This procedure is carried out, before the machine begins its operation.
Often, component placement machines are not born with sufficient control mechanisms to assure the feeding of correct components as desired by the user of these types of machines. Different solutions have been suggested where additional equipment is provided from a producer different than the producer of the machine and post-mounted on the machine. For such post-mounting, certain conditions in connection with the machines, as the mechanical structure, have to be taken into account. Often, the task is not to find the optimum solution generally, but to find the optimum solution under the given circumstances, that is to say to find the optimum solution for a given mechanical structure of the component placement machine. For example, some component placement machines have feeders on a platform or table that moves with respect to the pick-up system while others have a stationary table and a moving pick-up system. The control solutions are typically different for these two different types of machines.
A machine with an integrated control system is disclosed in Japanese patent application JP 2000 0223923 by Akira Tsunoda. This system is designed for a feeder system produced by Yamaha Motor Co Ltd, where a camera is mounted on the pick-up device and images the feeder identification close to the position where components are picked up. The system is used after installation of the feeders and before start of the industrial process for fabrication of the product. For use, the pick-up mechanism moves along the feeder table and images one feeder ID after the other, until all feeder IDs have been scanned. If a mistake is observed by the system, an alarm is sent to the operator for correction of the set-up. If the set-up is corrected, the system is used again for the control until the control reveals a correct installation of the feeders. This system has a number disadvantages. Firstly, this system is only suited for machines with sufficient space for mounting of a camera on the moving pick-up mechanism. Secondly, the feeder ID has to be placed relatively precisely in the vicinity of the pick-up region in order that the camera can image the ID. For a system integrated in a special machine, this is adaptable; however, several existing feeder machines do not have space at the pick-up region for mount of an ID. Therefore, this system is not suited for post-mounting. Thirdly, this system utilizes the machine information of the slot positions. As the machine is born with the control system, this utilizing is possible; however, such position information is usually not available for post-mounted systems. Fourthly, the procedure is performed before the start of the machine and in case of determined mistakes repeated before the start of the machine. Thereby, expensive time is wasted before the production start. Fifthly, if a number of feeders are placed wrongly in the machine, the time used for replacement of the feeder and a successive scan is multiplied. This can be understood from the following: a first error will be detected for the first wrongly placed feeder, after which a replacement has to be performed and a new scan has to be performed revealing the next wrongly placed feeder. This adds up to a long time before the machine is ready for operation. It would be desirable to provide a system not having these disadvantages.
A post-mounted control system has been disclosed in U.S. Pat. No. 6,027,019. In this system, two scanners are adapted to monitor the arrangement of slot markers and feeder markers in the machine while the machine is in operation. The slot marker and feeder marker are then compared with data in a device list. Such a control system is only suitable for existing machines, where the table is moveable while the pick up is stationary, because in many existing machines with movable pick-up systems, not enough space is left on the pick up for mounting a scanner on the pick-up. This system as described in U.S. Pat. No. 6,027,019 has another disadvantage in not being able to detect feeders with wrong components before the machine is started. An eventual error is first detected, after the first component has been picked up. If a component is wrong, expensive time is wasted until the machine is stopped and rearranged. A third disadvantage has also been observed for this system. As the table is moved, problems with reading of the feeder ID may occur in situations where a component from a special feeder is picked up from one edge of the feeder such that the feeder position is different than if the component would be picked up from the centre of the feeder.
For machines with stationary feeder platforms, a system is known, where each feeder is equipped with a transponder that is connected with the feeder by a chain. The transponder is inserted in a corresponding array platform behind the feeder for manual check whether the feeder is in the right slot. However, also this system has a drawback in not being able to prevent a misplacement of the transponder. The latter is due to the fact that feeders may be rather slim with the result of a hardly discernible correct position of two adjacent feeder positions in the platform.
For existing machines, no control solution has hitherto been proposed for taking into account the situation of the so-called splicing when a feeder only has a few components left on a tape. During splicing, the empty reel is taken out of the feeder without removing the remaining few components on the tape in the feeder. The tape with the remaining few components is then fastened—spliced—to a new tape with components rolled on a new reel, which then is inserted into the feeder. The advantage is that reels can be exchanged without having to exchange the feeder or stop the operation of the machine. However, no system has hitherto been provided to control whether a tape with correct components has been spliced to the tape with the remaining few components.